Lord Prescott has described coalition plans for police and crime commissioners across 41 police forces as "radical" and insisted that the elected posts "must not fetter" the operational independence of the police.

The former deputy prime minister's comments signalled a retreat from his words in an interview just days ago in which he indicated he believed that political interference in operational decisions was sometimes justified, as he discussed his intention to stand for one of the new roles.

Tim Brain, a former chief constable of Gloucester and visiting professor of criminology at Gloucestershire University, told BBC Radio 4's Today programme it was "almost certain" commissioners would interfere politically, under a system "designed by politicians, for politicians".

"I think it's going to be almost a racing certainty that we are going to see more political interference, but we are not going to see it obviously," said Brain. "The protocols, the law is very clear. The direction and control rests with the chief constable. What we are going to have is behind-the-scenes politicisation, probably not of this generation of chief constables but the next."

Prescott recently declared his intention to stand for a police and crime commissioner post in elections taking place in November and affecting 41 police forces in England and Wales, despite voting against the reform in parliament. He told the Independent on Monday: "The police always argue that [many things they do] are a matter of operations and politicians should not be involved. Well, I'm afraid I have a big argument with that."

But speaking to Today, he referred to the clear rules in place to ensure the chief constable "gets on with the job".

He said he was standing for the role because he wanted to play his part to get the "balance right" under a new structure designed to ensure communities have a greater say in police operations and which gives the elected individual a "statutory mandate to hold the police to account".

"That's never been done before," he said. "That's quite a radical reform. The Labour party didn't like this legislation and I voted against it, but once there is an election the party isn't going to stay out of it and they will want to see it doesn't go the way they feared it might go.

"The commissioner must not fetter the operational independence of the police force."

He said he believed he could express "the people's voice" in drawing up the five-year police plan with the chief constable.

"The roles are clearly defined in the protocol for the police to get on with the operational job," he said. "In developing the community plan, both the crime commissioner and the chief constable work out the plan for the security of the community. That is what is in the protocol. Once the plan is decided and the resources allocated, the chief constable gets on with the job."

Brain said fully elected police authorities would have been a better option than the new roles being introduced and dismissed the suggestion that the new system would increase contact with local communities as "absolutely nonsense".

"In fact it will decrease contact with local communities because of the size of some of these police force areas. West Midlands – more or less 3 million people – [is to have] diverse communities represented by one commissioner.